I think I solved Porpoising Problem
Being new to towing a TT ( hadna 5th wheel), the porpoising of my GMC HD 2500 was driving me crazy. Trailer weighs 8000 pounds and with the WDH set up by the dealer, the whole rig rode like crap. It ...
Forum Discussion
Porpoising is the compression of the TV's rear suspension (mainly) to have it
release the compressive energy at a frequency that matches the natural harmonics
of 'that' setup
Lots of things play in this. Shocks (the biggie), springs, rating of the TV RGAWR,
tongue/Pin weight, tires, WD Hitch system, with lots of etc's
Since a 9.1K GVWR, on the higher class TV's that normally has a higher natural
harmonic than a softer sprung for ride quality half ton (spans from around
6.2K up to 8.1K for the fake half tons)
Shocks 'dampen' the rate of change for the suspension. Installing higher rate
will help to solve, but ride quality will go down. If really heavy tongue/pin
then that will wear out the TV's rear shocks sooner
Changing the spring rates will also move the harmonic. Higher harmonic with higher
rate springs (leaf spring pack, coil springs, air bags, higher rate WD bars, etc)
Why you got lots of advice to change the spring rates, but most don't think it
that way...just increasing the overall spring rates is the norm
Increasing the WD bar tension and/or changing to higher rate bars, to even
reducing the WD tension moves the natural harmonic around
Moving the natural harmonic 'around' so that whatever is causing (expansion
joints, ruts, etc) 'that' harmonic will not be tuned into 'your' TV's natural
harmonic
Why changing tire pressure works on some, as that changes the harmonics.
Speeding up, or slowing down a ditto in changing the harmonics vs your setups
natural harmonic.
Ride quality isn't on my have to have list and close to the bottom of my nice
to have list...so on my setup have HD shocks (KYB Mono's). Harsh for most, but
okay for me and am noodling going double shocks soon (welding up my own kit)
release the compressive energy at a frequency that matches the natural harmonics
of 'that' setup
Lots of things play in this. Shocks (the biggie), springs, rating of the TV RGAWR,
tongue/Pin weight, tires, WD Hitch system, with lots of etc's
Since a 9.1K GVWR, on the higher class TV's that normally has a higher natural
harmonic than a softer sprung for ride quality half ton (spans from around
6.2K up to 8.1K for the fake half tons)
Shocks 'dampen' the rate of change for the suspension. Installing higher rate
will help to solve, but ride quality will go down. If really heavy tongue/pin
then that will wear out the TV's rear shocks sooner
Changing the spring rates will also move the harmonic. Higher harmonic with higher
rate springs (leaf spring pack, coil springs, air bags, higher rate WD bars, etc)
Why you got lots of advice to change the spring rates, but most don't think it
that way...just increasing the overall spring rates is the norm
Increasing the WD bar tension and/or changing to higher rate bars, to even
reducing the WD tension moves the natural harmonic around
Moving the natural harmonic 'around' so that whatever is causing (expansion
joints, ruts, etc) 'that' harmonic will not be tuned into 'your' TV's natural
harmonic
Why changing tire pressure works on some, as that changes the harmonics.
Speeding up, or slowing down a ditto in changing the harmonics vs your setups
natural harmonic.
Ride quality isn't on my have to have list and close to the bottom of my nice
to have list...so on my setup have HD shocks (KYB Mono's). Harsh for most, but
okay for me and am noodling going double shocks soon (welding up my own kit)
